Technical Field
The present disclosure relates to a semiconductor device and a semiconductor device manufacturing method.
Related Art
As the amount of ultraviolet radiation increases due to destruction of the ozone layer, there is growing concern today over the effect of the ultraviolet rays in sunlight on the human body and the environment.
Ultraviolet rays are classified into long-wavelength ultraviolet rays (UV-A: approximate wavelength of from 320 nm to 400 nm), medium-wavelength ultraviolet rays (UV-B: approximate wavelength of from 280 nm to 320 nm), and short-wavelength ultraviolet rays (UV-C: approximate wavelength of 280 nm and below), with each of these wavelength regions having a different effect on the human body and the environment. UV-A waves cause darkening of the skin, reach the dermis, and are a cause of skin aging. UV-B waves cause inflammation of the skin and may lead to skin cancer. UV-C waves have a strong germicidal effect, but UV-C waves are absorbed by the ozone layer and do not reach the surface of the earth.
Rapid notification of the daily amount of ultraviolet radiation is a matter of importance when it comes to protecting the human body. The UV index, which is an indicator of the amount of ultraviolet radiation, was introduced in 1995. The UV index is a measure of the relative impact on the human body, and may be calculated using the CIE action spectrum defined by the CIE (Commission Internationale de l'Éclairage/International Commission on Illumination).
Japanese Patent Application Laid-Open (JP-A) No. 2008-251709 proposes an ultraviolet ray receiving element capable of separating and detecting quantities of ultraviolet rays in two wavelength regions, UV-A waves and UV-B waves, so as to simplify the derivation of the UV index. This ultraviolet ray receiving element includes a silicon semiconductor layer having a thickness of from 3 nm to 36 nm formed above an insulating layer, lateral PN-junction type first and second photodiodes formed in the silicon semiconductor layer, an interlayer insulating film formed above the silicon semiconductor layer, a first filter layer configured from silicon nitride that is formed above the interlayer insulating film above the first photodiode and that transmits light having a wavelength in the UV-B wave wavelength region or longer, and a second filter layer configured from silicon nitride that is formed above the interlayer insulating film above the second photodiode and that transmits light having a wavelength in the UV-A wave wavelength region or longer.
Japanese Patent Application Laid-Open (JP-A) No. 2009-176835 describes an ultraviolet sensor including a filter film configured from a silicon nitride film that is formed on an interlayer insulating film above one photodiode and that transmits light having a wavelength in the UV-A wave wavelength region or longer, and a sealing layer that covers the interlayer insulating film and the filter film above another photodiode and that transmits light having a wavelength in the UV-B wave wavelength region or longer.
International Publication Pamphlet (WO) No. 2012/137539 describes an ultraviolet sensor including a filter on the light receiving face side of a light receiving element that transmits UV-A waves and UV-B waves.
The filter is configured by a multilayer film of alternatingly stacked low refractive index material and high refractive index material.
In JP-A2008-251709 and JP-A2009-176835, filters are configured using a single layer of silicon nitride film that, of UV-A waves and UV-B waves, blocks the UV-B waves and transmits the UV-A waves.
FIG. 1 is a graph, obtained by the present inventors, illustrating the spectral sensitivity of an ultraviolet sensor for cases in which a filter formed from a single layer of silicon nitride film is formed above the ultraviolet sensor. FIG. 1 illustrates cases in which a silicon nitride film (SiN) has a thickness of 100 nm and 200 nm, in addition to a case in which a silicon nitride film is not provided.
As illustrated in FIG. 1, providing a filter film formed from a single layer of silicon nitride film reduces sensitivity toward not only UV-B waves (approximate wavelength of from 280 nm to 320 nm), but also UV-A waves (approximate wavelength of from 320 nm to 400 nm). Namely, precise separation of UV-A waves and UV-B waves is considered to be difficult using a filter film formed from a single layer of silicon nitride film.